Browsing by Author "Elsayed, A. A"

Now showing 1 - 2 of 2

Influence of Silica Fume, Fly Ash, Super Pozz and High Slag Cement on Water Permeability and Strength of Concrete
(JORDAN UNIV SCIENCE & TECHNOLOGY, 2012-12) Elsayed, A. A
In this study, effects of mineral admixtures on water permeability and compressive strength of concretes containing silica fume (SF), fly ash (FA) and super pozz (SP) were experimentally investigated. Permeability of concrete was determined through DIN 1048 (Part 5). The research variables included cement type, ordinary Portland cement (OPC) or high slag cement (HSC), and mineral admixtures content was used as a partial cement replacement. They were incorporated into concrete at the levels of 5%, 10% and 15% for silica fume and 10%, 20% and 30% for fly ash or super pozz by weight of cement. Water-cement ratio of 0.40 was used and tests were carried out at 28 days. From the tests, the lowest measured water permeability values were for the 10% super pozz and 10% silica fume or 20% fly ash mixes. The highest compressive strength of concretes determined was for 10% silica fume mix with ordinary Portland cement and was reduced with the increase in the replacement ratios for other mineral admixtures than ordinary Portland cement concrete. The main objective of this research was to determine the water permeability and compressive strength of concrete containing silica fume, fly ash, super pozz and high slag cement to achieve the best concrete mixture having lowest permeability. The results were compared to those of the control concrete; ordinary Portland cement concrete without admixtures. The optimum cement replacement by FA, SP and SF in this experiment was 10% SP. The knowledge on the strength and permeability of concrete containing silica fume, fly ash, super pozz and high slag cement could be beneficial in the utilization of these waste materials in concrete work, especially on the topic of durability.
Study of Rock-Lining Interaction for Circular Tunnels Using Finite Element Analysis
(JORDAN UNIV SCIENCE & TECHNOLOGY, 2011) Elsayed, A. A
Finite element technique is used to model two phases of tunneling process, namely; excavation and rock-lining interaction. The excavation phase is responsible for determining the pre-lining rock mass deformations and the reduced in-situ stresses. The interaction phase models the compatibility of the rock-lining system. The deformations and stresses of the rock-lining system and the final rock mass pressure acting on the lining are determined. The finite element results are compared with the results of the Convergence-Confinement method for the case study (Shimizu Tunnel) that was guided by field measurements. One of the main objectives of this study is to investigate the effect of different parameters on the behavior of excavated tunnel before and after lining activation. The analysis followed the same procedure which had been applied in the analysis of the case of Shimizu Tunnel taking into consideration the different values of the tunnel radius and the depth of excavated tunnel through different qualities of rock ranging between poor, moderate and hard rock. The parametric study has been conducted for circular tunnel. The first lining system involved in this study was assumed to be shotcrete of thicknesses of 20, 30, 40 and 50cm, and the second lining system was steel ribs with shotcrete of thicknesses of 20, 30, 40 and 50cm. The results of Finite Element Analysis were presented for different thicknesses.